Judging by the more excited nationalist commentaries, one would imagine that the Yes campaign will shortly take the lead in the Scottish independence race. But today's TNS poll is a reminder of why the odds remain against it. Among those certain to vote, the Yes side is 13 points behind (46-33), while among all voters it is 12 behind (41-29). The No campaign's lead has narrowed from 14 points last month but not at the rate the SNP requires with just five months to go. (Although it's worth noting that some pollsters, most obviously Panelbase, show a smaller gap. Then again, others, such as YouGov, show a larger gap.)

The consolation for the nationalists is the large number of voters who remain undecided, with 30 per cent of all voters and 21 per cent of those certain to vote yet to be won over by either side.

If the Yes side is to triumph, it will need to overcome the traditional bias for the status quo in referendums (particularly in the closing stages) and reach further into the middle class heartlands of Unionism. Both remain formidable challenges.